1. Field of the Invention
The present invention relates to a charged particle microscope apparatus and an image acquisition method of a charged particle microscope apparatus.
2. Description of the Related Art
In a manufacturing process of a semiconductor wafer, miniaturization of patters multilayered on the wafer has progressed rapidly, and importance of a process monitor to monitor whether the patterns are formed on the wafer as designed has increased more and more. Recently, there are growing needs for confirmation of states of patterns buried under a surface through a process as well as patterns viewed on the surface or confirmation/measurement of a positional relation of such lower layer patterns and upper layer patterns exposed to the surface, due to complication of a minute pattern formation process by a limitation of exposure technology or changes in device structures.
As a tool for inspecting semiconductor pattern shapes, an optical inspection device based on bright field or dark field optical microscope technology or an inspection device of an electron beam type based on electron microscope technology has been widely used for managing a semiconductor wafer manufacturing line. Likewise, an optical type or an SEM type review device has been used when a detected defect is observed, and a scatterometry system or a scanning electron microscope for line width measurement using light has been used in a device for measuring pattern dimensions.
A dimension of a leading-edge semiconductor pattern has decreased to several-ten nanometer order and an inspection/measurement device developed from an electron microscope, particularly, a scanning electron microscope (critical dimension scanning electron microscope (SEM)) has been widely used to accurately recognize a state of the pattern or the defect.
However, in a general SEM that is used for semiconductor inspection/measurement in an in-line manner, only a pattern of an outermost surface of a sample can be observed. For this reason, the general SEM cannot be used to inspect or observe the buried layer.
In order to resolve the above problem, there have been some cases in which a lower layer pattern is inspected or measured by using an SEM having relatively high radiation energy. In “Feasibility Study for High Energy SEM-Based Reference Measurement System for Litho Metrology” by M. Bishop and D. Joy, Characterization and Metrology for ULSI Technology 2005, pp. 407-410 (2005), an example of the case in which a lower layer pattern is observed by increasing radiation energy an electron beam of an SEM, which is normally between several hundred eV to several keV and several ten keV is described.